Process of recovering copper oxide and a d-tartrate from a spinning solution



Dec. 5, 1950 H. HOFMANN 2,532,308

PROCESS OF RECOVERING COPPER OXIDE AND A D-TARTRATE FROM A SPINNING SOLUTION Filed Aug. a, 1946 K BLUE WASTE WASTE SKEIN WATER COPPER ACID WASH SOLUTIONS OVERFLOW SOLUTION f\ L r J i I i PRECIPITATING SLUR RY CONCENTRATING SLURRY M PREPARING LIVE STEAM /0 9K COPPER 0x10:

/2\ COPPER OXIDE w/a SLURRY EI HEM /4\ DISSOLVING & //8 C050 CuSO less $34: CRYSTALS n-TARTARIC ACID 2/ DECANTATION NA CO 2 a a PRECIPITATION WASHES 2 b-TARTARIC @El 25 ACID g 26 THREAD 1 IN V EN TOR.

HUGO HOFMANN AT TO RN EY l atent eci Dec. 5, 1950 SOLUTION AND A D-TARTRATE FROM A SPINNING Hugo Hofmann, Elizabethton, Tenn., ass'igfior, by mesrie assignments, to Beaunit Mills, Inc., New York, N. Y., a corporation of New York Application August 8, 1946, Serial No. 689,150

The present invention relates to a process of simultaneously recovering copper and tartaric acid in the form of salts from waste solutions formed during the manufacture of cuprammonium cellulose products, such as filaments, yarns, foils, films, etc.

One object of. this invention is the simultaneous recovery of copper salts and salts of tartaric acid in such a manner that the recovered chemicals can be used, in the production of cuprammonium cellulose spinning solutions.

Another object of the present invention is a process of simultaneously recovering copper oxide and tartrates of dextro (d-) tartaric acid in a facile and economical manner.

Other objects of the present invention will become apparent to those skilled in the art from a study of the following specification and drawing.

I am Well aware that many attempts have, heretofore, been made to recover copper and ammonia from waste spinning solutions and spin baths, such processes being disclosed for example in U. S. Patents Nos. 2,162,176; 2,300,883 and 2,184,923. However, this prior art does not disclose processes for the simultaneous recovery of copper salts and salts of tartaric acid, the very essence of the present invention. Spinning solutions used in the industry contain about 69% cellulose, 4-8% ammonia and 25% copper; and they may be prepared in accordance with processes set forth in U. S. Patent No. 1,728,565 and No. 1,974,273. In the so-called funnel stretchspinning process cuprammonium cellulose spinning solutions are extruded through the orifices of spinnerets mounted in funnels into substantially neutral water circulating therein. Such spinning processes are disclosed in U. S. Patents Nos. 1,828,497; 1,867,297; 1,871,704; 1,947,159 and 2,036,089. However, I wish to emphasize that my invention is not limited to this type of spinning since it can be used in the simultaneous recovcry of copper salts and salts of tartaric acid from any other waste solution containing the same. In order to improve the spinning of cuprammoniumcellulose solutions, it is necessary to add one or more stabilizing agents to the spinning solution, for example, tartaric acid which forms a tartrate therein. Tartaric acid occurs in four distinct modifications, namely: (1) dor dextrotartaric acid, (2) lor laevo-tartaric acid, (3) d-l or racemic tartaric acid and (4) ior inactive (meso-) tartaric acid. Although 1-, d-l, and itartaric acids are operative when added to cuprammonium cellulose solutions, nevertheless it has been found by exhaustive experimentation 2 Claims. (o1. 1ot 1s7) that dextro- (d-) tartaric acid offers outstanding advantages as an addition agent to such spinning solutions. It not only improves the spinning quality of cuprammonium cellulose solutions, but it prevents also to a large extent the formation of detrimental copper oxide deposits on the walls of the spinning funnels and nipples. The fact that the other tartaric acids enumerated above are much less efiective than d-tartaric acid may be due to steric hindrance, although I have been unable to prove this assumption with analytical means. I am well aware in this con nection that U. S. Patent No. 2,148,895 discloses the use of saccharic acid, etc., for the prevention of funnel deposits. Such acids, however, do not improve the spinning qualities of cuprammonium cellulose spinning solutions, although they do help to retard the formation of funnel deposits.

The invention is illustrated in the flow sheet constituting the single figure in the drawing. The alkaline water leaving the spinning funnels contains one or more copper salts apparently in com; bination with ammonia, a salt of tartaric acid and hydroxyl ions originating from the cupram monium' cellulose spinning solution, and it is called bluewater in the art. This blue water? i together with waste copper solutions for example, waste spinning solutions, 2 and other alkaline wastes herein referred to as alkaline waste waters form sources of the alkaline solutions used in the present recovery process. All of these waste copper solutions contain copper salts and tartrates. The cuprammonium cellulose solution 23 is extruded through the orifices of spinnerets into a plurality of funnels 28 to form a plurality of thread bundles 38 which are treated with, a dilute acid solution, for example sulphuric acid 3!. This acid hardens the still plastic threads and removes substantial amounts of copper salts and tartrate ions therefrom. This dilute acid solution is usually recirculated in order to maintain a substantially constant amount of copper and acid ions therein. A portion of this acid solution is removed from the circulating system. It is called waste acid overflow 3 and forms one source of the waste acid solutions used in this process. The treated thread bundles containing a plurality of filaments are wound in package or skein form 32 and treated with a dilute acid solution, for example sulphuric acid, 33, to remove more copper and 'tartrate ions therefrom before being Washed with water, The

Water running off from the packages orskeins called skein wash solutions 4, constitutes an other source of the waste acid solutions.

In accordance with the preferred embodiment of present invention, suitable amounts of blue water I, waste copper solutions, 2, waste acid overflow 3 and skein wash solutions 4 are mixed at about room temperature (15-30 C.) and a pH of about 6.4 to 7.8. This results in the precipitation of a slurry 5 containing copper and tartrate ions. The slurry is allowed to settle, and the solution overflow, containing soluble am.- monium salts, 6, is removed therefrom. The aforesaid overflow may be used in the recovery of ammonia therefrom. The slurry 5 is pumped into another settling tank 1 for further concentration. Overflow solution ,8 is run off from tank I, and chemicals may be recovered therefrom. The concentrated slurry is pumped into a re.- action vessel 9 and treated therein with caustic at an elevated temperature and a pH of about 10.5 to 11.0 to convert it into copper oxide while preserving the tartrate ions. Overflow solution I3 is removed, and chemicals may be recovered from this solution by suitable means. The copper oxide slurry I2 is removed vfrom vessel 9 to vessel 14 and converted therein by means of a suitable acid I5, preferably sulphuric acid, with heat 15, into a copper salt solution which contains also tartaric acid. Copper sulphate crystals 18 and tartaric acid I9 may be added to the solution to bring it to a proper copper and tartaric acid content. Subsequently a soluble alkali, for example, soda ash NazCOs 2|, is mixed with the copper salt solution IT in vessel 20 in an amount suflicient to precipitate the copper in the form of a basic copper salt, for example basic copper sulphate 20, and at the same time the tartaric acid in the solution is converted into a salt of tartaric acid. The precipitate is then decanted 22 preferably several times to remove soluble salts therefrom, and it may then be used in conventional manner in the production of cuprammonium cellulose solutions suitable for spinning. Such spinning solutions contain generally 6-9% cellulose, 4.8% ammonia and'25% copper. In addition such solutions should contain for the aforesaid reason also about 0.2-1.0 part of tartaric acid, preferably d-tartaric acid, calculated on the cellulose content'of the spinning solution.

Example I Copper Rate of Solutlon Content Flow Grams/liter Liters/min. Blue water 0. 107 43 Waste Acid Overflow 11.5 1.5 Waste Copper Solutions 0. 742 2.0 Skein Wash Solutions 0. 341 9. 0

The mixing process was controlled by'pH recordinginstrumenta'and a constant level of 1iq-. Hid was maintained in the mixing tank. A slurry was formed evidently comprising a mixture of cupric hydroxide, basic copper sulphate'and com!- plex copper tartrates. The mixture of slurry and solution was pumped into several basins in which the slurry was allowed to settle. The overflow (48.5 liters/min.) containing 0.023 gram of copper per liter was allowed to escape. The precipitated slurry, containing about 3.6 grams of copper per liter, was pumped at the rate of '7 liters per minute from the bottom of the basin into another settling basin where it was further concentrated. The overflow (1 liter/min.) containing 0.023 gram of copper per liter was allowed to run off. The concentrated slurry, containing about 4.2 grams of copper per liter, was pumped into a reaction vessel at the rate of 6 liters per minute into which a sufficient amount of a sodium hydroxide solution grs. NaOH/liter of water) was introduced together with open steam. Steam was used to heat the mixture for reasons of economy. The reaction vessel may be heated of course by other means to maintain the reacting temperature of about 60'75 C. The pH of the mixture was maintained between 10.5 and 11.0. A compact copper oxide was formed, which was pumped from the bottom of the reaction vessel into several settling basins. The overflow (6.9 liters/min.) containing 0.025 gram of copper per liter was run off. The compact copper oxide contained about 55% of the original tartrate used in the spinning solution. 77.8 kilograms of the compact copper oxide, 50.9 kilo.- grams of CuSO45H2O and 270 liters of a sulphuric acid solution (521 grams of H2804 per liter of water) :were mixed together with vigorous stirring at boiling temperature to form a copper sulphate solution. After cooling d-tartaric acid was added to compensate for the amount lost in the recovery process. After filtering, enough hot sodium carbonate solution was added to the copper sulphate solution to substantially precipitate all of the copper as :basic sulphate and the tartaric acid'in the form of a tartrate. The basic copper sulphate-tartrate mixture was used in the production of cuprammonium spinning solutions.

Example II Blue water, having the composition set forth in Example I, was mixed with a lime solution containing about 0.6 gram of calcium. Rate of flow of blue water was 21 liters per minute, and the lime solution flowed at a rate of 0.2 liter per minute to maintain a pH of about 10 to 10.5. The reaction was carried out at temperatures ranging from about 15'to 30 C. The reaction mixture was run into a settling tower, and a slurry was precipitated containing about 2.0 grams of copper per liter. This slurry was pumped at a rate of about 0.9 liter per minute into a reaction vessel together with the slurry obtained in accordance with the process set forth in Example I. The oxide was then worked up as set forth above. This modification allowed the working up of excess blue water obtained during spinning.

Although it is preferable touse sulphuric acid, sodium hydroxide and soda ash in my novel recovery process for reasons of economy, it is of course understood that other acids and alkalis may be used with equal success. Hydrochloric acid, potassium hydroxide, potassium carbonate are examples of equivalent compounds. Although it is advisable to combine all of the acid'and alkaline waste solutions for reasons of economy, nevertheless the recovery process can be carried out with one waste acid and one alkaline waste solution, for example blue water and waste acid overflow, etc. The recovered copper salt solutions may be treated in conventional manner to reduce the iron content thereof before precipitating the copper salt in the form of a basic copper compound.

Modifications and variations of this process will be apparent to those skilled in the art, and I desire to include all modifications and variations coming within the scope of the appended claims.

I claim:

1. The process of recovering a mixture of copper oxide and a tartrate from waste solutions occurrin in the manufacture of rayon involving the extrusion of a cuprammonium cellulose spinning solution containing d-tartaric acid in the form of ammonium d-tartrate into funnels in which slightly alkaline water is continuously circulated to form cellulose filaments and alkaline blue water as a waste product, combining said filaments to form a filament bundle, treating the filament bundle with an acid to extract copper therefrom in the form. of a soluble copper salt and with the formation of a waste acid containing said copper salt, d-tartaric acid and an ammonium salt, which comprises the steps in sequence of mixing said blue water with said waste acid at a pH of about 6.4 to 7.8 whereby a slurry containing essentially copper hydroxide and ammonium tartrate together with a supernatant solution containing essentially a salt formed by chemical interaction of said acid with ammonia contained in said cuprammonium cellulose solution is produced, allowing said slurry to settle and removing supernatant solution therefrom, further concentrating said slurry and further removing said supernatant solution therefrom, treating the thus concentrated slurry with caustic at an elevated temperature at a pH of about 10.5 to 11 to convert copper hydroxide into copper oxide while substantially retaining the d-tartrate therewith, and dissolving said copper oxide and d-tartrate in an acid to form a stock solution for utilization in the preparation of the cuprammonium cellulose spinning solution.

2. The process of recovering a mixture of copper oxide and a d-tartrate from waste solutions occurring in the manufacture of rayon involving the extrusion of a cuprammonium cellulose 6 spinning solution containing d-tartaric acid in the form of ammonium d-tartrate into funnels in'iwhich slightly alkaline water is continuously circulated to form cellulose filaments and alkaline blue water as a waste product, combining said filaments to form a filament bundle, treating the filament bundle with sulphuric acid to extract copper therefrom in the form of copper sulphate and with the formation of a waste acid containing said copper sulphate, d-tartaric acid and ammonium sulphate which comprises the steps in sequence of mixing said blue water with said waste acid at a pH of about 6.4 to 7.8 whereby a slurry containing essentially copper hydroxide and ammonium tartrate together with a supernatant solution containing essentially ammonium sulphate is produced, allowing said slurry to set tle and removing supernatant solution therefrom, further concentrating said slurry and further removing supernatant solution therefrom, treating the thus concentrated slurry with caustic at an elevated temperature at a pH of about 10.5 to 11 to convert copper hydroxide into copper oxide while substantially retaining the d-tartrate therewith, and dissolving said copper oxide and tartrate in an acid to form a stock solution for utilization in the preparation of the cuprammonium cellulose spinning solution.

HUGO HOFMANN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 866,371 Linkmeyer Sept. 17, 1907 1,049,201 Bronnert Dec. 31, 1912 1,490,499 Zart et a1. Apr. 15, 1924 1,920,208 Mutti Apr. 1, 1933 2,141,763 Richter Dec. 27, 1938 2,148,895 Becker Feb. 28, 1939 2,162,176 Kuss et al. June 13, 1939 2,322,778 Furness June 29, 1943 2,370,157 Furness Feb. 27, 1945 2,395,015 Schlosser et al. Feb. 19, 1946 FOREIGN PATENTS Number Country Date 144,295 Switzerland Dec. 3, 1930 

1. THE PROCESS OF RECOVERING A MIXTURE OF COPPER OXIDE AND A TARTRATE FROM WASTE SOLUTIONS OCCURRING IN THE MANUFACTURE OF RAYON INVOLVING THE EXTRUSIONOF CUPRAMMONIUM CELLULOSE SPINNING SOLUTION CONTAINING D-TARTARIC ACID IN THE FORM OF AMMONIUM D-TARTRATE INTO FUNNELS IN WHICH SLIGHTLY ALKALINE WATER IS CONTINUOUSLY CIRCULATED TO FORM CELLULOSE FILAMENTS AND ALKALINE BLUE WATER AS A WASTE PRODUCT, COMBINING SAID FILAMENTS TO FORM A FILAMENT BUNDLE, TREATING THE FILAMENT BUNDLE WITH AN ACID TO EXTRACT COPPER THEREFROM IN THE FORM OF A SOLUBLE COPPER SALT AND WITH THE FORMATIONOF A WASTER ACID CONTAINING SAID COPPER SALT, D-TARTARIC ACID AND AN AMMONIUM SALT, WHICH COMPRISES THE STEPS IN SEQUENCE OF MIXING SAID BLUE WATER WITH SADI WASTE ACID AT A PH OF ABOUT 6.4 TO 7.8 WHEREBY A SLURRY CONTAINING ESSENTIALLY COPPER HYDROXIDE AND AMMONIUM TARTRATE TOGETHER WITH A SUPERNATANT SOLUTION CONTAINING ESSENTIALLY A SALT FORMED BY CHEMICAL INTERATION OF SAID ACID WITH AMMONIA CONTAINED IN SAID CUPRAMMONIUM CELLULOSE SOLUTION IS PRODUCED, ALLOWING SAID SLURRY TO SETTLE AND REMOVING SUPERNATANT SOLUTION THEREFROM FURTHER CONCENTRATING SAID SLURRY AND FURTHER REMOVING SAID SUPERNATANT SOLUTION THEREFROM, TREATING THE THUS CONCENTRATED SLURRY WITH CAUSTIC AT AN ELEVATED TEMPERATURE AT A PH OF ABOUT 10.5 TO 11 TO CONVERT COPPER HYDROXIDE INTO COPPER OXIDE WHILE SUBSTANTIALLY RETAINING THE D-TARTRATE THEREWITH, AND DISSOLVING SAID COPPER OXIDE AND D-TARTRATE IN AN ACID TO FORM A STOCK SOLUTION FOR UTILIZATION IN THE PREPARATION OF THE CUPRAMMONIUM CELLULOSE SPINNING SOLUTION. 